The present invention relates generally to a fuel injector and more particularly to improvements in the design of fuel injectors utilizing needle guides.
Conventional fuel injectors utilize external filters to remove particulates from the fuel as it approaches the fuel injector""s inlet. While such filters are suitable for preventing particulate material in the fuel from entering the fuel injector, they are incapable of filtering particulate material that may originate internally within the fuel injector. Particulates may originate within the fuel injector due to manufacturing, assembly or through usage of the fuel injector.
It is known that filters may be located within the fuel injector between the inlet and the internal valve. It is optimal to locate the filter as close to the internal valve as possible so as to catch particulates originating internally in the fuel injector. It is also known that a filter may be located on top of a lower needle guide to filter the fuel at a position just above the internal valve.
The lower needle guide, that can be used to position such a filter, is a known element located above the valve seat. The lower needle guide commonly contains a center guide bore that receives the injector needle passed there through. The center guide bore insures that the injector needle is properly seated on the valve seat when the fuel injector is in the closed position. In one known embodiment, the valve guide contains several large passage bores surrounding the center guide bore to allow fuel to pass through the needle guide to the internal valve. An internal filter is located on top of the needle guide to filter fuel before it passes through the large passage bores in the needle guide. Fluid can only pass through the areas of the internal filter located directly above the large passage bores leaving sections of the filter unused. This design is inefficient since only portions of the filter can be utilized. It would be desirable to have a design with a more efficient filtering system.
In addition to inefficiency, the known embodiment has further disadvantages. The addition of a filtering element can require tight manufacturing tolerances and precise assembly procedures. The filter and the needle guide must be aligned properly to prevent contact between the filter element and the injector needle. Improper assembly, manufacture, or post assembly movement of the filter can cause contact with the injector needle. Contact with the injector needle can cause unwanted friction in the movement of the injector needle. Such undesired friction may result in undesirable wear and possible performance problems of the injector needle. It is therefore desirable to have an internal filter design that eliminates the assembly requirements and alignment problems that can lead to interference with the injector needle.
It is also known that introducing swirl turbulence in the fuel as it passes through the fuel injector is desirable since it improves the atomization of the fuel and thereby improves the fuel injector performance. In several known embodiments, the swirl turbulence is induced through the use of elements located downstream of the valve seat. Placing swirl turbulence elements downstream of the valve seat can require an increase in the volume of space downstream the valve seat. Increasing the volume of space downstream the valve seat can increase hydrocarbon emissions. A major goal of the automotive industry has been to minimize hydrocarbon emissions. It is therefore desirable to induce swirl turbulence without the need to increase the volume of space downstream of the valve seat.
One known method of increasing swirl turbulence without increasing the volume of space downstream of the valve seat is by inducing swirl in the fuel as it passes through the valve guide. In a known design, a tangential flow is induced as the fuel is passed through the valve guide. Such designs have not contemplated the use of non-tangential flow swirl such as micro-swirl to improve fuel atomization. In addition, such designs require a separate filter element and therefore are subject to the efficiency, assembly and alignment problems that are associated with the addition of a separate filter element to the fuel injector. It would therefore be desirable to retain the swirl turbulence characteristics of the known tangential flow swirl design while allowing for non-tangential swirl and adding filtering characteristics that do not cause efficiency, assembly or alignment problems.
It is therefore an object of the present invention to provide a fuel injector with a needle guide that combines the characteristics of a conventional valve guide and filter element into a single element whereby the efficiency of the filter is increased, the assembly requirements of the fuel injector are minimized, and friction transmitted to the injector needle is reduced. It is a further object of the present invention to provide a valve guide that induces swirl turbulence in the fuel passing through it without increased hydrocarbon emissions or increased manufacturing costs associated with known designs.
In accordance with the objects of this invention, a fuel injector is provided. The fuel injector includes a housing. Located within the housing is an armature assembly which includes an injector needle. The injector needle is movable between a closed position and an open position. The injector needle remains in contact with a valve seat when the injector needle is located in the closed position.
The fuel injector includes an orifice disc located downstream of the valve seat. The orifice disc contains one or more orifice metering pathways to direct fuel passing through the orifice disc towards a desired location.
The fuel injector also includes a needle guide located upstream of the valve seat. The needle guide contains a bore through which the injector needle passes. The bore keeps the injector needle properly positioned on the valve seat to insure a proper seal when the injector needle is located in the closed position. The needle guide also contains a plurality of filtering passageways to allow fuel to pass through the needle guide. Each of the plurality of filtering passageways is of a smaller cross-sectional area than each of the one or more orifice metering pathways located in the orifice disc to prevent particulates larger than the metering pathways from passing through the needle guide. The sum of the areas of the plurality of filtering passageways is greater than the sum of the areas of the one or more orifice metering pathways to insure adequate flow through the fuel injector. The plurality of filtering passageways may be formed at angles relative to the injector needle to force swirl turbulence in the fuel passing through the needle guide.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.